The commercial introduction of polychlorinated biphenyls (PCBs) in 1929 represented a major breakthrough in the technology of dielectric fluids. These compounds were found to have outstanding thermal stability, resistance to oxidation, acids, bases and other chemical agents, as well as excellent electrical insulating characteristics making them ideal for applications in electrical capacitors and in high performance electrical transformers. PCBs gained rapid and widespread acceptance in the electrical industry.
In 1966, the discovery of PCBs in environmental samples stimulated concern over, and considerable research on their potential toxic hazards. By the early 1970's those hazards had become well recognized, and prompted major manufacturers of PCBs to restrict sales to applications in closed electrical systems. All production of PCBs was stopped in 1977.
During the 1970's the U.S. Environmental Protection Agency (EPA) set out to develop guidelines for control of PCBs. This effort culminated in publication of a series of regulations on PCBs handling and disposal requirements in the Federal Register on May 31, 1979 and Mar. 28, 1980. See also: "EPA's Final PCB Ban Rule: Over 100 Questions and Answers to Help You Meet These Requirements", Office of Toxic Substances, EPA, Washington, D.C. (June 1980). These regulations cover the maintenance, operation, and disposal of three classes of transformers, as follows:
Below 50 ppm--Noncontaminated [Non-PCB Transformer] PA1 50 ppm to 500 ppm--PCB Contaminated Transformer PA1 Above 500 ppm--PCB Transformer;
the higher the concentration of PCBs in the transformer, the stricter the regulations.
These regulations have had particular impact on electrical utility companies. Although PCBs have not been used extensively in general purpose distribution transformers, cross contamination in transformer manufacturing and service facilities over many years has resulted in widespread appearance of relatively small amounts of PCBs in many transformers.
The development of acceptable procedures for operating under the EPA regulations has become the subject of intensive research. The principal effort has been directed toward development of safe and effective PCB disposal techniques. Until recently the only accepted methods of disposal were by dumping in rigidly designed safe land fills or burning in carefully controlled high temperature incinerators. However, lack of approved facilities has limited disposal capacity by these methods. Such methods are also wasteful and reslt in permanent decommissioning of transformers or destruction of valuable and relatively scarce dielectric fluids.
Because of their remarkable stability PCBs are not only resistant to biological degradation but also to most of the well-known chemical decomposition methods. Some chemical decontamination methods which have reportedly produced positive results suffer from one or more serious limitations. The most widely reported chemical methods for decomposing PCBs employ extremely reactive sodium compounds. Sodium in liquid ammonia has long been used for this purpose in analytical chemical laboratories. Other decomposition processes for PCBs which are claimed to be effective employ high surface sodium, sodium/naphthalene, and sodium naphathalide. These processes share some notable drawbacks. The reagents are difficult to prepare, expensive to ship and unstable in storage. Moreover, active sodium compounds are sensitive to oxygen and to water and therefore cannot be used reliably under field conditions.
A few combined chemical/physical methods of PCB disposal have also been reported. See: O. Hutzinger, et al., "The Chemistry of PCBs", CRC Press Cleveland, Ohio, (1974). For example, radiation can destroy PCBs under certain conditions, but the process is slow, inefficient and not readily adaptable to field use. Some polymers, such as chloroprene derivatives, have been used to absorb PCBs from oil but these also apparently have limited effectiveness because of very low absorption capacity and very slow absorption rate.
During the past several years the Franklin Research Center of the Franklin Institute, Philadelphia, Pa. has developed a proprietary system for stripping the chlorine substituents from PCBs, thus rendering them non-toxic and readily disposable. More specifically, Pytlewski, Krevitz and Smith, in their U.S. patent application Ser. Nos. 142,865 and 158,359, filed Apr. 21, 1980 and June 11, 1980, respectively, disclose and claim a method for the decomposition of halogenated organic compounds, especially PCBs, which represents a significant advance over the aforementioned methods of the prior art. The decomposition reagent used in practicing that method is produced by reacting an alkali metal, a liquid reactant, such as a polyglycol or a polyglycol monalkyl ether, and oxygen. This reagent produces virtually complete dehalogenation of a variety of halogenated organic compounds, simply by mixing it with the halogenated compound in the presence of oxygen. Additional details of the methods of preparation and use of the previously discovered decomposition reagent are set forth in the two applications identified above, the entire disclosures of which are incorporated herein by reference as though set forth herein in full.
In U.S. patent application Ser. No. 240,622, filed Mar. 5, 1981, the entire disclosure of which is also incorporated herein by reference as though set forth herein in full, there is described and claimed another invention by the same inventors based on the discovery that decomposition of halogenated organic compounds may be carried out using a reagent produced by the reaction of an alkali metal hydroxide (rather than an alkali metal), a liquid reactant, such as a polyglycol or a polyglycol monalkyl ether, and oxygen. This decomposition reagent gives results which are comparable to those obtained with the method described in the earlier filed applications referred to above.
The reagents of the aforesaid copending applications are collectively referred to hereinafter as NaPEG reagents, or simply NaPEG.
The development of the NaPEG reagents has made it possible to remove PCBs from fluids contaminated therewith, as well as to decompose PCBs in a safe, efficient and effective manner.